


Fireworks

by AlasPoorYorcake



Category: Undertale (Video Game)
Genre: M/M
Language: English
Status: Completed
Published: 2020-07-06
Updated: 2020-07-06
Packaged: 2021-03-04 20:48:18
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,423
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25102678
Author URL: https://archiveofourown.org/users/AlasPoorYorcake/pseuds/AlasPoorYorcake
Summary: During a slow day in the lab, Sans picks Gaster’s brain about some human thing that’s been nagging him. Established Sanster, Sans POV, Fluff.
Relationships: W. D. Gaster/Sans
Comments: 3
Kudos: 53





	Fireworks

* * *

“hey, boss?”

Gaster doesn’t look up from his paperwork. You can barely see him past the stacks of paper and your own feet, which you’ve propped up on your desk. 

You toss a crumpled piece of paper at him. A conjured hand bats it out of the way. 

“Must you?” he mumbles.

“what’re fireworks?”

He stops writing for a brief moment. Then he shakes his head and resumes. “Have you ever fought a moldsmal?”

“m’not really the fightin’ type.”

“Of course not. My apologies,” he says insincerely. And then doesn’t elaborate.

You stare at him, but as always, he’s got the Underground’s worst case of tunnel vision. His hand is moving so fast over the forms you can barely see it. “k. so. you gonna tell me why you’ve been bullying moldsmals?”

“What?” That gets him to look up. Finally. “I have not been _bullying_ moldsmals.”

“no, see, ‘cause i was wondering why i don’t see them around anymore.”

“That would be because they prefer Waterfall’s marshy climate. The temperature at which moldsmals melt is far below the average temperature of Hotland.”

You turn sly eyelights on Gaster.

“…melting point.”

“Yes, melting point. Hell, without the CORE stabilizing the air currents, I presume it would even get hot enough to reach their boiling point. Hence their absence,” he says, and adds, “ _Not_ because I have been ‘bullying’ them.”

“‘course not. you’ve just been _melting_ them.”

“Sans.”

“jeez, doc. how many moldsmals have to go before your reign of terror is complete?”

“The majority of moldsmals have a traditional bullet pattern reminiscent of fireworks,” Gaster growls. “If you keep talking, I will be sure to give you a demonstration.”

“there ya go. that wasn’t so hard, was it?”

He glares at you. At least, you think he does— his expression’s hard to read, given that his permagrin is different than you or your brother’s. It leaks lacivious intent at random intervals, especially when his eyes go all half-lidded like that. 

Not that you would ever tell him that.

You’d rather just admire from a distance.

He goes back to his paperwork. You crumple up another piece of paper and toss it between your hands. You wait just long enough for the silence to get comfortable.

“alright, doc. you’re killin’ me. tell me already.” You shoot the paper towards his desk. He catches it mid-air with a conjured hand.

“Perhaps if you would stop lobbing confidential documents at me, I could tell you.” 

“they’re reports based off bad data. fruits of a poisonous tree, an’ all that. shredding ‘em is as pointless as keeping ‘em.”

“Of course. After all, why shred them when you can just as easily make projectiles out of them to pester me with?”

You wink. “they told me you were a smart one.”

Gaster sighs, putting down his pen to scrub at his face with two real hands, cored palms and all. “It’s one hundred and twelve degrees fahrenheit, if you must know. Do _not_ ask me how many unfortunately itinerant moldsmals I have had to transport back to Waterfall in a beaker.”

“uh. heh. yikes. nice image, but not what i was fishin’ for,” you say. The expression he shoots you is blank. Probably. You splay your fingertips. “ _fireworks_ , doc. fireworks.”

“Ah.”

“any day now.”

“Yes, yes. Fireworks were explosives the humans were quite fond of using during festivities and the like. They would make colorful… patterns in the sky. They were also terribly loud.”

“wait, so they just sent stuff up in the sky and blew it up ‘cause it looked nice?”

“Essentially.”

“huh,” you say, sliding your feet off your desk. “sounds kinda like us.”

His permagrin might not allow for many clear expressions, but it’s perfect for incredulity. “How on earth did you come to that conclusion?”

“well, think about it. potentially dangerous things flying through the air in patterns ‘cause it’s pretty?” You scoff. “i know i don’t use bullet patterns that much in my day-to-day, but i know ‘em when i hear ‘em.”

Gaster hums. He’s got that stillness that always comes over him when he’s thinking through a problem. He’d solidify completely if he thought it would make his thoughts faster. “I suppose there are similarities. I wouldn’t be surprised if fireworks were the product of human envy over our traditional patterns.”

“or maybe they just liked the look of them.”

“Possibly.”

“well, it sounds to me like you don’t like ‘em.”

“Humans?”

You splay your fingers. “ _fireworks_ , doc. fireworks.”

“Yes, of course. I mean— no, I did not like them back when I was. Er. Younger.”

“mm.” You nod slowly. “…think you’d like ‘em now?”

“I couldn’t say for—” You physically see the thought hit him. It’s better than drugs. “…certain. Oh, dear.”

“yeah, doc?” If you weren’t grinning since birth, you’d be splitting your skull trying to smile even wider.

“Sans,” he says.

“yup,” you say.

“Do you have fireworks,” he says.

“yup,” you say.

“Where did you get them,” he says.

“the dump,” you say.

He takes a deep breath. And then another. And another. “How… did you even know what they’re called?”

“i’m gonna call that a lucky guess.” 

From your pocket, you pull out one of the rocket-shaped things and toss it to Gaster. Despite his earlier dexterity with the paper balls, he fumbles the explosive. It slips straight through his palm.

When he picks it up, the look on his face is priceless. You know why— the word ‘fireworks’ is branded on the side of the rocket in faded lettering.

“I can’t believe this,” he says. He quick to correct, “I can’t believe _you_. This— this isn’t even _damp_.”

“yeah. i found ‘em a couple days ago, figured i’d let ‘em dry. wanted to ask you about ‘em in the meantime.”

“Wh— they’ve been _in your pocket_ this whole time?”

“uh. yeah?”

“Sans, you work in a lab that _is surrounded by lava_.”

“that’s why i _kept_ them in my _pocket_ , doc. c’mon. it ain’t rocket science.”

Gaster flattens you with a vaguely lascivious glare. “This is unbelievably reckless, Sans. Do you know what could have happened if one of these had fallen out of your pocket?”

“nope. actually, i was kinda hopin’ to find out. y’know. once i got ahold of someone who knows what they’re doin’.”

“You—” And then he stops, because he’s always speaking faster than he’s thinking, and sometimes it takes him a minute. “You wanted to set them off. With… me.”

“uh, sure? i thought watchin’ them was the point,” you say, “but yeah. thought it’d be a cute date idea.”

“But this,” he says, and then, “I don’t,” and finally, after another deep breath: “Okay. I suppose… that sounds… fine.”

“fine,” you repeat. “heh. doc, we don’t have to.”

“I… No, I think I would like to.”

“you think.”

Gaster sighs. “I am not as young as I used to be, Sans. Reckless fun caveats responsibility and consequences. It is hard to think past them.”

“you tryin’ to tell me you’re not impulsive?”

“…You have a point.”

“hey. what can i say? we skeletons are pointy dudes.” And then, because you care, “c’mon. you know your comfort zone better than anyone i know, doc. just say the word.”

Gaster appraises you for a long moment. Being skeletons, a relationship doesn’t come with much touching, or even proximity. But time is something Gaster values above anything else— and sometimes it baffles you that he chooses to spend so much of it paying attention to you.

The staring is edging you closer to mushy territory. You can’t look away.

“The word,” he says finally, “is that I would like to spend my evening watching fireworks with you.” Except he says it like he means _every evening_ , and you don’t know if you can take this. “As long as you’ll have me.”

“…k.” It seems the melting point of your soul is embarrassingly low. Your voice sounds a little like you swallowed a vat of melted moldsmal slime. “guess that’s settled.”

“Indeed,” he says evenly. You’re pretty sure he knows exactly what he’s doing to you. Cheeky bastard. “We will not, however, be setting off dangerous explosives after work if we do not finish working.”

“yup.”

“Please use the shredder this time.”

“right.”

“And Sans?”

“yep.”

“I love you.”

Your soul boils in its cage. 

Bastard, bastard, _bastard_. Not for the first time, your permagrin feels too small for the smile you feel bursting in your soul.

“yeah,” you say, helpless. “love you too, doc.”

* * *

**Author's Note:**

> <3


End file.
